1. Field of the Invention
The present invention relates to an apparatus for patterning a functional material, and more particularly to an electrically conductive pattern forming apparatus utilizing an electrophotographic process.
2. Description of Related Art
In recent years, as an alternative technique for a photolithograph method comprising an expensive mask and a multistage process, an electrically conductive pattern forming method based on a printing process with a simple process such as an intaglio printing method, a relief printing method, a screen printing method, a dispenser, inkjet printing, or electrophotographic printing attracts attention. Any of the processes uses a conductive particle dispersed solution in which conductive particles are dispersed in a solvent, or a toner in which conductive particles are doped in a resin, and achieves patterning by indirect coating using a printing plate or a screen, direct coating by nozzle scanning, or electrostatic attraction to an optional electrostatic latent image. Then, by heating and burning this, the fine particles are fused with each other to become a conductor to obtain wiring.
Among the above described various printing processes, the electrophotographic method which forms a desired electrically conductive pattern on an insulating substrate by using electrostatic force is especially adaptable to mass production and formation of a large area pattern since a roll enables continuous production. Further, since it is easy to change an electrically conductive pattern, which is advantageous for large item small scale production, there are many advantageous points as compared with the other processes. As an electrically conductive pattern forming method using an electrophotographic method, there are known a method in which a dry toner with conductive particles doped in a resin is patterned on a substrate with high heat resistance such as a ceramics green sheet, and then heated at a high temperature to remove the resin component and fuse metal components (see JP-A-11-251718, for example), and a method for forming a electrically conductive pattern by performing plating in which metal particles in a toner after patterning are used as nuclei (see JP-A-2004-48030, for example). However, when the dry toner as described above is used, the minimum particle diameter limit of the toner which can be handled in the air is 5 μm or more from the viewpoint of powder dust prevention, and it is physically impossible to form an electrically conductive pattern of 10 μm or less, for example.
In connection with the above described problem, there are proposed some patterning techniques which handle fine powder of an electrically conductive material in a state of an electrically conductive fine particle dispersed solution in which the fine powder is dispersed in a solution, that is, some electrically conductive pattern forming techniques based on liquid development (see JP-A-2006-278801 and JP-A-2002-527783, for example). Since the problem of fly powder dust which exerts influence on environment and human bodies can be solved by handling the particles in a solution, it becomes possible to handle the conductive particles having a nano-scale particle diameter, and to realize not only pattern formation with high definition, but also direct handling of conductor particles without possibly using a resin component which becomes ion adsorption charge in the solution to cause high resistance (JP-A-2006-278801, for example).